Some biopsy devices include a tubular cutting element or cannula having a body tissue cutting distal end, and a stylet slidable in the cannula and having a pointed distal end for piercing tissue and a cavity for receiving tissue to be sampled. In using such a device, the stylet and cannula are relatively positioned so that the distal end of the cannula covers the cavity and closely surrounds the distal end of the stylet to prevent the coring of tissue during insertion into the patient. In one method of using such a device, the stylet and cannula are inserted to a position either in the tissue from which a sample is to be taken or to a point adjacent such tissue. The cannula may then be held stationary with one hand, while the stylet is moved distally with the other hand so that the distal end and the cavity of the stylet move into tissue from which a sample is to be taken. Next, the stylet is held stationary with one hand while the cannula is moved distally thereby cutting tissue that has moved into the cavity. With the tissue sample within the cavity and covered by the cannula, the stylet and cannula are removed from the patient. The body tissue sample may then be removed from the biopsy device for testing purposes.
The above procedure is somewhat complicated and there is the danger of inadvertently moving the wrong member at the wrong time. Because the two members are at times movable together and other times movable relative to each other in performing the biopsy, the person performing the biopsy may inadvertently fail to use the proper sequence of movements or steps in effecting the above procedure. This can, in some cases, result in damage to the patient or failure to obtain a sample thereby requiring a second insertion.
With some biopsy devices it is possible to inadvertently insert the cannula and stylet while the cannula cutting tip is distally of the stylet tip and this would result in damage to body tissue due to coring.
To correct these problems, the invention disclosed in U.S. Pat. No. 4,702,261 to Cornell et al. was invented, the teachings of which are incorporated herein in their entirety as if completely recited herein. In accordance with one aspect of the '261 invention, a biopsy device is provided which includes a cutting member having a cannula which has a distal cutting end, the cannula slidably receiving a stylet having a cavity near the distal end thereof adapted for receiving sample material to be cut by the cannula. The biopsy device includes a housing in which the cannula and stylet members are movable. The '261 device includes means for limiting relative longitudinal movement between the actuators for preventing the distal end of the cutting element from extending distally beyond the distal end of the stylet.
In accordance with another aspect of the '261 invention, a biopsy device is provided which includes a housing, and stylet and cannula members having actuators that are longitudinally slidable relative to each other and the housing, and are disposed in parallel side-by-side relation. An attachable handle may be used.
In accordance with another aspect of the '261 invention, a method of taking a biopsy sample is provided which includes utilizing a biopsy device having a cannula member with a distal cutting end and a stylet member having a cavity and a tissue piercing distal end. The distal ends are inserted into the patient. While holding the housing stationary with one hand, the stylet is advanced to allow tissue to enter the cavity, and then while holding the housing stationary, the cannula is advanced to sever tissue and provide a tissue sample in the stylet cavity.
However, a problem with the prior art biopsy devices is that once a tissue sample has been collected in the stylet cavity, the entire device must be removed from the tissue in order to retrieve the sample. Thereafter, if it is desirable to obtain additional samples, the cannula and stylet must be again inserted into the patient before a sample can be collected. This additional reinsertion of the cannula and stylet very often leads to additional cutting of the patient's tissue. Therefore, it is desirable to create a biopsy device which can take multiple samples without having to reinsert the cannula into the patient for every sample.